the f-b-i is leading the investigation. here is what we know right now. police say, at least three people were killed in the blasts -- one victim, an eight year old boy. more than 140 others were injured. the explosions were about a block apart - and happened within seconds of each other. some victims lost limbs, suffered broken bones, shrapnel wounds and ruptured eardrums. of those hurt, officials say, at least 15 are in critical condition. police have no suspects in custody. however, police are searching an apartment in a boston suburb. in connection to the deadly blasts. officials in washington say, there has been no immediate claim of responsibility -- but the attack is being treated as an act of terrorism. what's still not clear is whether it is a domestic or foreign act. kron4's grant lodes takes a closer look at the pair of explosions near the boston maraton finish line. the amount tonight, a dramatic video of the first explosion. tonight, this was filmed by a boston globe a photographer and let me warn you that some of these images are horrific >>